Having unsaturated double bonds, a conjugated diene polymer is inferior in heat stability, weatherability, and ozone resistance. Methods for improving these properties by hydrogenating the unsaturated double bonds have long been known. Such methods are disclosed, e.g., in JP-B-48-30151 (The term “JP-B” as used herein means an “examined Japanese patent publication”), JP-A-52-96695 (The term “JP-A” as used herein means an “unexamined published Japanese patent application”), JP-A-56-30401, and JP-B-59-37294.
The characteristics of these hydrogenated polymers are taken full advantage of when blended with thermoplastic resins such as polyolefins or other rubbery polymers to find broad applications as thermoplastic resin modifiers or in the field of automobile parts.
For example, JP-A-56-30447 discloses a composition comprising: a hydrogenation product of a conjugated diene polymer having a vinyl bond structure of 40% or more in the diene moiety; and an α-olefin polymer, and JP-A-2-36244 discloses a composition comprising: a hydrogenation product of a conjugated diene polymer having a vinyl bond structure of 10% or more; and a thermoplastic resin.
These disclosed hydrogenation products have poor anti-blocking and, when formulated into a resin composition, provides a composition with considerably poor rigidity.
It has recently been attempted to hydrogenate a conjugated diene polymer having a vinyl bond-rich block and a vinyl bond-poor block in the polymer chain.
For instance, JP-A-56-30455 discloses a composition comprising: a hydrogenation product of a diblock copolymer comprising a first block having not more than 15% by weight 1,2-microstructure and a second block having at least 30% by weight 1,2-microstructure; and an α-olefin polymer. JP-A-3-128957 proposes a thermoplastic elastomer composition comprising: a hydrogenated diene polymer obtained by hydrogenating a block copolymer comprising a polybutadiene block segment having a 1,2-vinyl bond content of not more than 20% by weight and a block segment comprising a butadiene unit portion having a 1,2-vinyl bond content of 25 to 95% by weight; and a thermoplastic resin and a rubbery polymer. JP-A-8-109288 teaches a composition comprising: a hydrogenation product of a block copolymer having conjugated diene polymer blocks having a difference of 15% by weight between the maximum vinyl bond content and the minimum vinyl bond content; and a polyolefin.
However, resin compositions containing these block copolymers are still insufficient in balance between low-temperature impact resistance and rigidity, failing to meet the recent increasing demand for resin compositions having well-balanced physical properties. It has been keenly desired to develop a hydrogenated conjugated diene polymer which, when formulated into compositions, will achieve excellent balance between impact resistance and rigidity and excellent elongation characteristics.
An object of the present invention is to provide a hydrogenated polymer having a specific structure which is excellent in anti-blocking and processability and, when blended with other thermoplastic resins or rubbery polymers, provides compositions having well-balanced physical properties and excellent moldability.
Another object of the invention is to provide a process for producing the hydrogenated polymer having a specific structure.
A still other object of the present invention is to provide a composition of the hydrogenated polymer and other thermoplastic resins or rubbery polymers which is excellent in balance between low-temperature impact resistance and rigidity, elongation characteristics, and moldability.